Train dispatching system for railroads



Jan. 2 1937.

O. H. DICKE TRAIN DISPATCHING SYSTEM FOR RAILROADS Filed April 12;, 1923VE 0R Y "I'TORNEY Patented Jan. 26, 1937 FATE??? FEQE TRAIN DISPATCHINGSYSTEM FOR RAILROADS Application April 12, 1928, Serial No. 269,388

24 Claims.

This invention relates to train dispatching systems, and moreparticularly to the type of system in which a dispatcher communicateswith an engineer of a moving train through the medium of signalindications.

In a system of the type mentioned the track switches at passing sidingsare preferably operated by switch machines controlled by the dispatcher,and these track switches preferably have signals associated therewithfor indicating to the engineer of an approaching train whether he is totake the main track or siding; and if he is headed away from the sidinginforming him when he may proceed. By reason of the fact thatinformation must be transmitted to the engineer either through cab orwayside signals provision must be made to transmit many distinctiveindications to each passing siding. If wayside signals are used eachpassing siding would require 20 at least eight signals and if theswitches are to be power operated two switch machines are preferablyemployed. It is thus important that these various controls betransmitted over the least number of line wires, such line wires alsoaiiord ing means for communicating to the dispatchers office theexistence of traflic conditions at such passing siding.

In accordance with the present invention it is proposed to use a singleline circuit to transmit 30 such distinctive controls, such line circuitbeing applied to a railway signalling system having an alternatingcurrent transmission line associated therewith. This single linecircuit, in addition to said transmission line, forming the medium forcontrolling all of the switch machines and signals associated with asingle passing siding and also afiording a medium through which toinform the dispatcher when there is a train passing over a particulartrack switch of such passing siding.

More specifically it is proposed to apply alternating current potentialof one or another relative polarity, direct current potential of one oranother polarity or both of these potentials to the line circuit, and tohave connected in series with each other (or in multiple if desired) apolarized alternating current relay and a polarized direct current relayat the corresponding passing siding, whereby either of these relays maybe energized to either of their energizing conditions irrespective ofthe condition of the other relay. In addition it is proposed to connectin series with the line circuit but located in the dispatchers office adirect current and an alternating current indicating relay, and toprovide means at the passing siding for impeding or stopping the flow ofdirect or alternating current or both, depending upon which of the twodetector track circuits associated with the two track switches of thepassing siding are occupied or whether both of these track circuits areoccupied, whereby one or the other or both of the indicating relays inthe dispatchers ofiice will be deenergized and will light indicatinglamps corresponding to the occupancy of the particular detector trackcircuit or circuits.

Other objects, purposes and characteristic features of the inventionwill in part be obvious from the accompanying drawing and in part bepointed out in the specification hereinafter.

In describing the invention in detail reference will be made to theaccompanying drawing conventionally illustrating the apparatus in thetower and the apparatus associated with one passing siding only of arailway system having the invention applied thereto.

Referring to the accompanying drawing the invention has been shownapplied to one passing siding PS only, of a railway system having alarge number of passing sidings, which railway system may be either adouble track system or it may be a single track system employing waysidesignals of the absolute-permissive type, it being understood that therest of the passing sidings employ duplicate apparatuses except as tothe alternating current transmission line TL energized by a generatorGand the common return wire CL, which lines extend through the entireportion of the railway system governed by a single dispatcher located inthe dispatchers office DO. Referring particularly to the railway systemthe track rails 3 of the main track and the rails l of the siding aredivided into block sections in the usual way by insulating joints 5, soas to constitute the usual track circuits each including a track relayand a source of current. Of these detector relays the detector trackrelay DTE and DTW only have been shown, and these have been shownconventionally by dotted lines.

The entrance of a train into the east end of the track or side track ofthe passing siding PS is governed by the main signal I and thetakesiding signal I and the departure of a train from the main track andside track, respectively, is governed by the starting signals 2 and 2Similarly, the entrance and departure of trains at the west end of thepassing siding PS is governed by signals 1, i 8 and 8 The east end ofthe passing siding PS includes a track switch ES and the west end ofthis same passing siding includes a track switch WS. These trackswitches are preferably operated by switch machines through the mediumof control relays DC and AC all in a manner as more clearly pointed outin the application of S. N. Wight, Ser. No. 120,423 filed July 3, 1926which control mechanisms and circuits are conventionally shown by dottedlines I 4 and I5 through contacts 4d of these relays. Similarly, thesignals I, I 2, 2 I, I 8, and 8 are controlled in accordance with thecondition of contacts 45 of the control relays DC and AC and inaccordance with the position of the track switches ES and WS, in amanner as described in said Wight application, and as shownconventionally by dotted lines l6, l1, I8 and I 9. The present inventionrelates principally to the manner in which the polar control relays ACand DC are controlled from a distant dispatchers ofiice over the sameline Wire, and how the occupancy of detector track circuits containingtrack relays DTW and DTE are transmitted to the dispatchers ofiice overthis same line wire, and for this reason the control circuits for theswitch machines and the signals associated therewith controlled by thecontrol relays AC and DC have not been specifically illustrated. In thisconnection it may also be pointed out that the way-side signals may beentirely omitted and the dispatching information transmitted to theengineer through the medium of signals located in the engine cabcontrolled in any suitable manner, as for instance, shown in Fig. 19 ofsaid Wight application.

At the west end of the passing siding PS is provided a control relay ACof the three-position type, which is preferably a relay responsive onlyto alternating current and of either the dynamometer or induction type,having its one winding connected in series with the line wire LW andhaving its other winding connected across the AC transmission line TL.Similarly, there is located at the east end of the passing siding PS athree-position or polar control relay DC, which preferably includeseither a permanent magnet or a locally energized direct currentelectro-magnet and which relay has its winding connected in series withthe line LW. The control relay AC is controlled in accordance with theposition of the lever WL having contacts Ill and I I, and the controlrelay DC is controlled by a lever EL having contacts l2 and I3. In thedispatchers ofiice is also located a miniature track layout having apassing siding ps and including, among other things, miniatureindicating lamps IW and IE, which indicate the condition of occupancy ofthe detector track circuits associated with the west and east end of thepassing siding PS, respectively. The various features of the presentinvention are believed best understood by considering the operation ofthe system.

Operation-With the levers WL and EL, located in the dispatchers officeD0, in their neutral normal position, as shown,.the way-side signalsassociated with such levers are in the stop position shown, this forreason more clearly pointed out in the Wight application above referredto. Also, with these levers WL and EL in their normal neutral position,the indicating lamps IW and IE associated with the miniature passingsidings ps are extinguished. This is the case in spite of the fact thatthe contacts 55 and 42 of the indicating relays ACI and DCI are closed,and is true because their energizing circuits are open at contacts Illand I2, respectively.

Let us assume that there is a west-bound train approaching the passingsiding PS and that the dispatcher wishes this train to take the maintrack and proceed through the passing siding. To accomplish this, thedispatcher will move his lever EL to the right, and since the trackswitch is already in the main track position this track switch will notbe operated, but the signal I will be caused to assume its clearposition, providing trafiic conditions in advance are clear, thisbecause the control relay DC is energized toward the right hand maintrack position through the following circuit:beginning at the battery29, wire 2 l Winding of the indicating relay ACI, wire 22, winding ofthe indicating relay DCI Wires LW and 23, winding of the relay AC, Wire24 contact 25 of the detector track relay DTW Wires 25 and 21, frontcontact 28 of the detector track relay DTE, wire 29, winding of thecontrol relay DC (causing this relay to assume its right-hand energizedposition) wires 36, CL and BI, contact H of the lever WL, wires 32 and33, contact I3 of the lever EL in its right-hand position, wire 33 backto battery 20.

With this circuit completed, not only is the control relay DC energizedto its right-hand position but the indicating relay DCI, which respondsonly to direct current, also assumes its right-hand position, and forthis reason the indicating lamp IE is not illuminated even thoughcontact I2 has been closed. If the West-bound train in question is topass through the passing siding PS, as has been assumed, the signal Imust also be clear. In order to clear the signal I the dispatcher willmove his lever WL to the right-hand position and in so doing willmomentarily open the circuit which was just traced but will complete thesame circuit with the righthand portion of the secondary winding oftransformer T connected in series therewith. In other words, alternatingcurrent of a particular relative polarity is superimposed upon thedirect current flowing in the line circuit. This AC current will causecontrol relay AC to assume its righthand energized position, thuscausing the signal I to assume its clear indicating condition, providingtrafiic conditions in advance are favorable. Not only is the alternatingcurrent relay AC energized but the indicating relay ACI is likewiseenergized to its right-hand position, thereby maintaining the indicatinglamp IW extinguished in spite of the closure of contact Id.

Let us now assume that the west-bound train in question passes thesignal I, and in so doing treads on the detector track circuitcontaining the track relay DTE. The entrance of the train on thedetector track circuit containing this track relay DTE causes thecontact 28 thereof to drop thereby deenergizing the control relay DC.This dropping of the contact 28 will, however, not cause deenergizationof the control relay AC because the substituted partial circuitcomprising, wires 37 and all, condenser 38 and inductance 39, has thecapacities of the condenser and induc tance so chosen that the two unitsin series are resonated to the frequency of thealternating currentemployed, so that the flow of alternating current there through is notmaterially, if at all,

diminished. The line circuit as now changed includes the condenser 38 inseries, and for this reason direct current cannot flow in this circuiteven though this circuit has impressed thereon direct current potentialsupplied by the battery 20, and the direct current indicating relay DCIwill assume its deenergized condition and will cause illumination of theindicating lamp IE through the following circuit:beginning at theterminal B of a suitable current source, such as a battery, contact 22of the lever EL, wire 41, contact 42 of the indicating relay DCI, wire13, indicating lamp IE to a common return C connected to the other sideof such battery.

The illumination of the indicating lamp IE informs the dispatcher thatthe train in question is entering the east end of the passing siding PS.As soon as the rear end of the train clears the detector track circuitcontaining the track relay DTE the indicating lamp IE is againextinguished for obvious reasons. As the train in question enters uponthe detector track circuit containing track relay DTW at the west end ofthe passing siding PS, it causes dropping of the contacts 25 and 46thereby causing the control relay AC to be shunted through thesecontacts 25 and 46 in series, and also causes the original line circuitto be broken at the front point of contact 25. Dropping of contact 46,however, reestablishes the circuit slightly modified by inserting thetuned unit, comprising the inductance 50 and the condenser 5| inmultiple, in series with the line wire LW.

With the unit Fall-51 tuned to potential resonance, as distinguishedfrom current resonances, included in series with the line wire LW thealternating current is decreased to such a value that the indicatingrelay ACI assumes its deenergized position, thereby completing thefollowing circuit for illuminating the indicating lamp IW:-beginning atthe terminal B of a suitable battery, contact ll) of lever WL in itsright-hand position, wire 54, contact 55 of the indicating relay ACI inits deenergized condition, wire 56 indicating lamp IW to the commonreturn wire C connected to the other side of said battery. Thedispatcher is thus informed by the illumination of the indicating lampIW that the westbound train is now occupying the detector track circuitcontaining the track relay DTW.

Let us assume that at this time, namely, with the detector track relayDTW deenergized, there is a following train entering upon the detectortrack circuit containing detector track relay DTE, and that both ofthese detector track relays assume their deenergized position. Underthis condition the line circuit includes both alternating and directcurrent potential, but the constants of the circuit are such as to allowno direct current and very little alternating current to flow. This linecircuit with both levers to the right and both detector track relaysdeenergized may be traced as follows:beginning at the secondary windingof the transformer T, wire 33, contact l3 of the lever EL, wire 34,right-hand portion of battery 20, wire 2!, winding of indicating relayACI, wire 22, winding of indicating relay DCI, wires LW and 60, contact46 of the detector track relay DTW in its deenergized condition, wires6i and 52, the unit 5!35l tuned to potential resonance (restricting flowof alternating current), wires 63 and 21', contact 28 of the detectortrack relay DTE in its deenergized condition, wire 3?, condenser 38,(blocking the flow of direct current) inductance 39, wires 49, CL and3|, contact H of the lever WL in its right-hand position, back to theright-hand terminal of the secondary winding of transformer T.

No direct current can flow in the circuit just traced for the reasonthat the condenser 38 is in series therewith, and very little, if any,alternating current can flow in this circuit by reason of the tuned unit58-5! tuned to potential resonance is included in series therewith. Forthis reason, both of the indicating relays ACI and DCI will assume thedeenergized condition and the indicating lamps IW and IE will beilluminated, indicating to the dispatcher that both of the detectortrack circuits of the passing siding PS are occupied.

Obviously, if the lever LE is moved to the lefthand position directcurrent of the reverse polarity will flow and the control relay DC isenergized to the left-hand position. Likewise if the lever LW is movedto the left-hand position the alternating current supplied to the lineLW is of reversed relative polarity as compared with the local windings65 and 6B of the relay ACI and AC, respectively, and therefore theserelays A01 and AC will assume their left-hand energized position. It is,of course, understood that with the control relay AC or DC energized tothe left-hand position the corresponding track switch is operated by asuitable switch machine SMW or SME to the take siding position, in whichevent the corresponding dwarf signal of takesiding signal is cleareddepending on the direction of trafiic set up.

In connection with the direction of trafiic just mentioned, it is to beunderstood that the direction of trafiic travel is determined by thesequence of operation of the various levers located in the dispatchersofiice through interlocked relays, all in a manner as described indetail in the Wight application above referred to.

Although switch machines have been conventionally shown, it should beunderstood that the invention may be applied to systems where the trackswitches are thrown by hand or where spring switches are used.

Having thus shown rather conventionally and described how two switchmachines and eight signals may be controlled, and the condition ofoccupancy of two detector track circuits may be indicated, over a singleline circuit, in any combination or sequence of controls and indicationswithout interference, and having shown how train movements may begoverned over an entire railway system by a single dispatcher, it is tobe understood that the particular circuit arrangements and devicesselected have not been chosen to illustrate the scope of the inventionor the particular arrangement preferably employed in practicing theinvention, but have been selected for the purpose of illustrating thenature of the invention in a simplified and direct way; and it isfurther desired to be understood that changes, modifications andadditions may be made to adapt the invention to the particularconditions encountered in practicing the same, all without departingfrom the spirit and scope of the invention or the idea of meansunderlying the same, except as demanded by the scope of the appendedclaims.

What I claim is:-

1. In a train dispatching system, the combination with a line circuitcontaining a relay responsive only to alternating current and a relayresponsive only to direct current in series and located at a distant waystation, means at a local dispatchers ofiice for applying alternatingcurrent or direct current or both to the line circuit including saidrelays in series, an alternating current indicating relay and a directcurrent indicating relay located at said dispatchers oifice connected inseries with said line circuit, and means at said way station forstopping the iii) flow of direct current without interfering with theflow of alternating current or reduce the flow of alternating currentwithout interfering with the flow of direct current to causede-energization of one or the other of said indicating relays.

2. In a train dispatching system, the combination with a railway signalsystem including a passing siding, signals associated with each end ofsaid passing siding; a relay responsive only to current of one characterfor controlling the signals at one end of said passing siding; a relayresponsive to current of another character for controlling the signalsat the other end of said passing siding; a dispatchers ofiice; twoindicating relays in said dispatchers office one responsive only to saidcurrent of one character and the other responsive only to current ofsaid another character; a circuit including all of said relays whichcircuit if energized by current of one character will cause the tworelays responsive thereto to assume the energized position and ifenergized by current of said another character will cause the remainingtwo relays to assume an energized position; means at the dispatchersoffice for energizing said circuit with current of said one character,current of said another character, or currents of both characters; andmeans at said passing siding for blocking the flow of current of onecharacter without blocking the flow of current of said anothercharacter.

3. In a train dispatching system, the combination with a railway signalsystem including a passing siding, signals associated with each end ofsaid passing siding, a relay responsive only to current of one characterfor controlling the signals at one end of said passing siding, a relayresponsive to current of another character for controlling the signalsat the other end of said passing siding, a dispatchers office, twoindicating relays in said dispatchers oflice one responsive only to saidcurrent of one character and the other responsive only to current ofsaid another character, a circuit including all of said relays whichcircuit if energized by current of one character will cause the tworelays responsive thereto to assume the energized position and ifenergized by current of said another character will cause the remainingtwo relays to assume an energized position, means at the dispatchersoffice for energizing said circuit with current of said one character orcurrent of said another character or currents of both characters, andmeans at said passing siding for blocking the flow of current of eithercharacter without blocking the flow of current of the other character.

4. In a train dispatching system, the combination with a railway signalsystem including a passing siding, signals associated with each end ofsaid passing siding, a relay reponsive only to current of one characterfor controlling the signals at one end of said passing siding, a relayresponsive to current of another character for controlling the signalsat the other end of said passing siding, a dispatchers oifice, twoindicating relays in said dispatchers oifice one responsive only to saidcurrent of one character and the other responsive only to current ofsaid another character, a circuit including all of said relays whichcircuit if energized by current of one character will cause the tworelays responsive thereto to assume the energized condition and ifenergized by current of said another character will cause the remainingtwo relays toassume an energized condition, means at the dispatchersoffice for energizing said circuit with current of said one character orcurrent of said another character or currents of both characters, andmeans at said passing siding for blocking the flow of current of onecharacter only, blocking the flow of current of the other character onlyor blocking the flow of current of both characters depending on trafiicconditions of said passing siding.

5. In a train dispatching system, the combination with a railway systemincluding a passing siding; signals associated with each end of saidpassing siding; a relay responsive only to current of one character forcontrolling the signals at one end of said passing siding; a relayresponsive to current of another character for controlling the signalsat the other end of said passing siding; a dispatchers ofiice; twoindicating relays in said dispatchers office one responsive only to saidcurrent of one character and the other responsive only to current ofsaid another character; a circuit including all of said relays whichcircuit if energized by current of one character will cause the tworelays responsive thereto to assume the energized condition and ifenergized by current of said another character will cause the remainingtwo relays to assume an energized condition; means at the dispatchersofiice for energizing said circuit with current of said one character,current of said another character or currents of both characters; andfiltering means in said circuit and at said passing siding forpermitting the flow of current of one character while restricting theflow of current over another character.

6. In a train dispatching system, the combination with a railway signalsystem including a passing siding, signals associated with each end ofsaid passing siding, a relay responsive only to current of one characterfor controlling the signals at one end of said passing siding, a relayresponsive to current of another character for controlling the signalsat the other end of said passing siding; a dispatchers ofiice, twoindicating relays in said dispatchers oflice one responsive only to saidcurrent of one character and the other responsive only to current ofsaid another character, a circuit including all of said relays whichcircuit if energized by current of one character will cause the tworelays responsive thereto to assume the energized condition and ifenergized by current of said another character will cause the remainingtwo relays to assume an energized position, means at the dispatchersofiice for energizing said circuit with current of said one character ofsaid another character or currents of both characters, filtering meansat said passing siding for permitting the flow of current of onecharacter without permitting the fiow of current of said anothercharacter, and means for rendering said filtering means active undercertain conditions of traffic only.

7. In a train dispatching system, the combination with a railway signalsystem including a passing siding, signals associated with each end ofsaid passing siding, a relay responsive only to current of one characterfor controlling the signals at one end of said passing siding, a relayresponsive to current of another character for controlling the signalsat the other end of said passing siding, a dispatchers oifice, twoindicating relays in said dispatchers oflice one responsive only to saidcurrent of one character and the other responsive only to current ofsaid another character, a circuit including all of said relays whichcircuit if energized by current of one character will cause the tworelays responsive thereto to assume the energized condition and ifenergized by current of said another character will cause the remainingtwo relays to assume an energized condition, means at the dispatchersofiice for energizing said circuit with current of said one character ofsaid another character or currents of both characters, two filteringdevices the first restricting the flow of current of one character andpermitting the flow of current of the other character, and the secondrestricting flow of current of said another character but permitting theflow of current of said one character, and means for rendering one orthe other of said filtering devices active depending on trafiicconditions.

8. In a train dispatching system; the combination with a railway signalsystem including a passing siding; signals associated with each end ofsaid passing siding; a relay responsive only to current of one characterfor controlling the signals at one end of said passing siding; a relayresponsive only to current of another character for controlling thesignals at the other end of said passing siding; a dispatchers office;two indicating relays in said dispatchers oflice one responsive only tocurrent of one character and the other responsive only to current ofsaid another character; a circuit including all of said relays whichcircuit if energized by current of one character will cause the tworelays responsive thereto to assume the energized condition and ifenergized by current of said another character will cause the remainingtwo relays to assume an energized condition; means at the dispatchersoffice for energizing said circuit with current of said one character,of said another character or currents of both characters; and twofiltering devices, the first of which restricts the flow of current ofone character and permits the flow of current of the other character,and the second of which restricts the flow of current of the othercharacter but permits the flow of current of said one character, andmeans for rendering one or the other or both of said filtering devicesactive depending on trafiic conditions.

9. In a train dispatching system; the combination with a railway signalsystem including two track switches comparatively close together;signals associated with each of said track switches; a relay responsiveonly to alternating current for controlling the signals at one trackswitch; a relay responsive only to direct current and controlling thesignals at the other track switch; a dispatchers office; two indicatingrelays in said dispatchers office, one responsive only to alternatingcurrent and the other responsive only to direct current; a circuitincluding all of said relays, which circuit if energized by alternatingcurrent will cause the two alternating current relays to assume anenergized condition, and if energized by direct current will cause theremaining two relays to assume the energized condition; means at thedispatchers ofilce for energizing said circuit with alternating current,or direct current, or both alternating and direct current; and means atsaid two sidings for blocking the flow of alternating current withoutblocking the flow of direct current, or vice versa.

10. In a train dispatching system the combination with a railway signalsystem including two track switches comparatively close together,signals associated with each of said track switches, a relay responsiveonly to alternating current for controlling the signals at one trackswitch, a relay responsive only to direct current and controlling thesignals at the other track switch, a dispatchers office, two indicatingrelays in the said dispatchers ofiice, one responsive only toalternating current and the other responsive only to direct current, acircuit including all of said relays which circuit if energized byalternating current will cause the two alternating current relays toassume an energized condition and if energized by direct current willcause the remaining two relays to assume the energized condition, meansat the dispatchers office for energizing said circuit with alternatingcurrent or direct current or both alternating and direct current, andmeans at the two sidings for blocking the flow of either alternating ordirect current without blocking the flow of the other current.

11. In a train dispatching system the combination with a railway signalsystem including two track switches comparatively close together,signals associated with each of said track switches, a relay responsiveonly to alternating current for controlling the signals at one trackswitch, a relay responsive only to direct current and controlling thesignals at the other track switch, a dispatchers ofiice, two indicatingrelays in the said dispatchers ofiice, one responsive only toalternating current and the other responsive only to direct current, acircuit including all of said relays which circuit if energized byalternating current will cause the two alternating current relays toassume an energized condition and if energized by direct current willcause the remaining two relays to assume the energized condition, meansat the dispatchers ofice for energizing said circuit with alternatingcurrent or direct current or both alternating and direct current, andmeans at said two sidings for blocking the flow of either direct oralternating current or blocking the flow of both alternating and directcurrent.

12. In a train dispatching system the combination with a railway signalsystem including two track switches comparatively close together,signals associated with each of said track switches, a relay responsiveonly to alternating current for controlling the signals at one trackswitch, a relay responsive only to direct current and controlling thesignals at the other track switch, a dispatchers oifice, two indicatingrelays in the said dispatchers office, one responsive only toalternating current and the other responsive only to direct current, acircuit including all of said relays which circuit if energized byalternating current will cause the two alternating current relays toassume an energized condition and if energized by direct current willcause the remaining two relays to assume the energized condition, meansat the dispatchers oifice for energizing said circuit with alternatingcurrent, with direct current or both alternating and direct currents,and filtering means in said circuit and near said two track switches forpermitting the flow of direct current while restricting the flow ofalternating current or vice versa.

13. In a train dispatching system the combination with a railway signalsystem including two track switches comparatively close together,signals associated with each of said track switches, a relay responsiveonly to alternating current for controlling the signals at one trackswitch, a relay responsive only to direct current and controlling thesignals at the other track switch, a dispatchers ofiice, two indicatingrelays in the said dispatchers oflice, one responsive only toalternating current and the other responsive only to direct current, acircuit including all of said relays which circuit if energized byalternating current will cause the two alternating current relays toassume an energized condition and if energized by direct current willcause the remaining two relays to assume the energized condition, meansat the dispatchers office for energizing said circuit with alternatingcurrent, with direct current or both alternating and direct current, andfiltering means at said two track switches for permitting the flow ofdirect current while restricting the flow of alternating current or viceversa, and means for rendering said filtering means active to havedifferent filtering characteristics depending on traflic conditions.

14. In a train dispatching system the combination with a railway signalsystem including two track switches comparatively close together,signals associated with each of said track switches, a relay responsiveonly to alternating current for controlling the signals at one trackswitch, a relay responsive only to direct current and controlling thesignals at the other track switch, a dispatchers office, two indicatingrelays in the said dispatchers office, one responsive only toalternating current and the other responsive only to direct current, acircuit including all of said relays which circuit if energized byalternating current will cause the two alternating current relays toassume an energized condition and if energized by direct current willcause the remaining two relays to assume the energized condition, meansat the dispatchers oilice for energizing said circuit with alternatingcurrent or direct current or both alternating and direct current, andtwo filtering devices, the first restricting the flow of alternatingcurrent and permitting the flow of direct current and the secondrestricting the flow or" direct current while permitting the flow ofalternating current, and means for rendering one or the other of saidfiltering devices active depending on traflic conditions.

15. In combination, a circuit including two relays one of which isresponsive only to current of one character and the other of which isonly responsive to current of another character; means for including asource of energy of said one character, of said another character, orsources of both said characters in said circuit; and controllable meansfor blocking the flow of current of said one character without blockingthe flow of current of the said another character.

16. In combination, a circuit including two relays one of which isresponsive only to current of one character and the other of which isonly responsive to current of another character means for including asource of energy of one character, or another character, or sources ofboth characters in said circuit; controllable means for blocking theflow of current of one character Without blocking the flow of current ofthe other character; and other controllable means for blocking the flowof current of said other character without blocking the flow of currentof said one character.

17. In a system of the character described, a track circuit, a signalgoverning traffic over said track circuit, a relay for controlling saidsignal, a control circuit for said relay governed from a distant point,means including said control circuit and responsive to the flow ofdirect current in said circuit for maintaining an indicating circuit atsaid distant point open while said track circuit is unoccupied, andother means responsive to alternating current flowing in said controlcircuit for indicating the occupancy of another track circuit.

18. In a train dispatching system, the combination with a siding, adetector track circuit at one end of said siding, signals governingtraffic over said siding, a control relay, a line circuit controlledfrom a distant control point, manually operable means at said controlpoint for energizing and de-energizing said line circuit to control saidrelay, means for opening said line circuit while said detector trackcircuit is occupied, an indicating lamp at said distant control pointlighted so long as said detector track circuit is occupied and saidmanually operable means is in a position to energize said line circuit,another track circuit, and another indicating means including a sourceof alternating current rendered active when another track circuit nearsaid siding is occupied.

19. In a dispatching system or the character described, a line circuitextending from a central control point to a distant siding and having acontrol relay therein, a manually operable circuit controller and asource of current for energizing said line circuit and located at saidcentral control point, a direct current indicating relay at the centralcontrol point in said line circuit, an alternating current indicatingrelay at said central control point included in said line circuit,indicating means rendered active while said direct current indicatingrelay is de-energized and said circuit controller is operated, anotherindicating means controlled by said alternating current relay, a trackrelay at said siding acting when deenergized to open said circuit tode-energize said direct current relay and another track relay at saidsiding for blocking the flow of alternating current in said line circuitto effect de-energization of said alternating current relay.

20. In a train dispatching system, the combination with a railway trackhaving adistant passing siding including a track switch at each endthereof, a switch machine for each of said track switches, signalsassociated with each of said switch machines for directing the movementof trams into and out of each end of said passing siding, a localdispatchers ofiEice, a line circuit connecting said dispatchers ofliceand said passing siding and including in series two direct currentresponsive relays and two alternating current responsive relays one ofeach class of said relays being located at said siding and one of eachclass of said relays being located at said dispatchers ofiice, means atsaid dispatchers ofiice for energizing said direct current relays orsaid alternating current relays or both said direct current relays andsaid alternating current relays, means at said passing siding forrestricting the flow of direct current only, alternating current only,or both direct and alternating current in accordance with 'trackoccupancy at one end, at the other end, and at both ends of said passingsiding respectively, means for controlling the signals associated withone of said track switches by the direct current relay at said passingsiding and controlling the signals associated with the other trackswitch by the alternating current relay at said passing siding, andsignals in said dispatchers office controlled by said relays in saiddispatchers oflice.

21. In a train dispatching system, the combination with a railway trackhaving a passing siding, of a track switch associated with said passingsiding, signals associated with said passing siding, a switch machinefor operating said track switch, a dispatchers ofiice, a line circuitconnecting said dispatchers office and said passing siding, a directcurrent responsive relay included in said line circuit and located nearsaid switch machine for operating said switch machine, an alternatingcurrent responsive relay included in said line circuit and located nearsaid signals for operating said signals, and means at said dispatchersoffice for independently operating said direct current and saidalternating current relay or operating said relays simultaneouslythrough the medium of said line circuit.

22. In a train dispatching system, the combination with a railway trackhaving a passing siding, of a track switch associated with said passingsiding, signals associated with said passing siding, a switch machinefor operating said track switch, a dispatchers ofiice, a line circuitconnecting said dispatchers ofiice and said passing siding, a directcurrent responsive relay included in said line circuit and located nearsaid switch machine for operating said switch machine, an alternatingcurrent responsive relay included in said line circuit and located nearsaid signals for operating said signals, means at said dispatchersoffice for independently operating said direct current and saidalternating current relay or operating said relays simultaneouslythrough the medium of said line circuit, means at said dispatchersofiice distinctively detecting the flow of direct and alternatingcurrent in said line circuit, and means at said passing siding fordistinctively blocking the flow of direct or alternating current in saidline circuit.

23. In combination with a railway switch and a signal for governing themovement of traffic over said switch, a first manually operable lever,

a second manually operable lever, a pair of line wires extending from apoint adjacent said levers to a point adjacent said switch, a firstsource of current, a second source for supplying current of a differentcharacter than current supplied by said first source, means forcontrolling the operation of said switch by current from said firstsource supplied to said line wires by said first lever, means forcontrolling said signal by current from said second source supplied tosaid line wires by said second lever, two track sections, a trackcircuit for each of said sections each including a track relay, a firstapproach indication means controlled through a contact of the first ofsaid track relays by current from said first source supplied to saidline wires by said first lever, and a second approach indication meanscontrolled through a contact of the second of said track relays bycurrent from said second source supplied to said line wires by saidsecond lever.

24. In a traffic controlling system for railroads; a local ofiice and adistant way station; traffic controlling devices at said way station;two distinctive current responsive control relays at said way stationfor controlling said trafilc controlling devices; two distinctivecurrent responsive indication relays at said office; a pair of linewires connecting said oflice and way station and interconnecting saidrelays; two correspondingly distinctive sources of current at saidoifice; means for applying one, the other or both of said distinctivesources of currents to said pair of line wires to energize one, theother or both of said control relays; and traffic controlled meanslocated at said way station for, when both of said sources of currentare applied to said pair of line wires, controlling the flow of eitherof said sources of current through its corresponding indication relaywithout interfering with the flow of the other distinctive current.

OSCAR H. DICKE.

